It has been common practice in plastic, otolaryngological and other surgeries for many years to inject or place within tissues a variety of artificial substances to repair or reconfigure anatomic structures. For example, Teflon polytetrafluoroethylene) particles have been introduced into the vocal cords and more recently into periureteral and periurethral tissues with mixed results. Disadvantages associated with this procedure include long-term progressive foreign body reactions and migration and distant embolism associated with very small particles. Considerable research has been conducted to discover substitutes for Teflon and other conventionally employed artificial materials.
Bio-active glasses have been utilized as bone replacement materials in a variety of reconstructive surgical techniques. These glasses have been shown to develop a strong bond with hard tissue because of a series of ion exchange reactions between the implant surface and body fluids that result in the formation of a biologically active calcium phosphate film at the implant tissue interface. See Hench et al, J. Biomed. Mater. Res., Vol. 5, pp. 117-141 (1971), and Hench et al, J. Biomed. Mater. Res., Vol. 7, pp. 25-42 (1973). Bio-active glasses have also been shown to form firm bonds with soft tissue. See Wilson, et al, J. Biomed. Mater. Res., Vol. 15, pp. 805-817 (1981); Wilson and Merwin, J. Biomed. Mater. Res.: Applied Biomaterials, Vol. 22, No. A2, pp. 159-177 (1988); and Wilson, Low et al, Biomaterials and Clinical Applications, Ed. by Pizzoferrato et al, Elsevier Science Publishers B. V., Amsterdam (1987).
Certain bio-active and bio-compatible glasses and glass-ceramics, e.g., those described in U.S. Pat. Nos. 4,159,358; 4,234,972; 4,103,002; 4,189,325; 4,171,544; 4,775,646; 4,851,046, and 5,074,916 (all incorporated herein by reference), have been shown to develop a unique, strongly adherent, chemical bond with hard tissue (bone) tissue due to the influence on hydroxyapatite of the biologically active calcium phosphate film generated in situ by ion-exchange reactions between the glass or glass-ceramic surface and body fluids. This influence results in a strong fixation of the glass or glass-ceramic to the bone surface. Although as noted above, a variety of such glasses have been shown to bond to various soft tissues, it has been found that several of these glasses result in the formation of an exceptionally thin (i.e., no more than about 1-3 fibers thick), but adherent collagen film which strongly adheres the glass to soft tissue without concomitant adverse side effects.
Failure to observe soft tissue bonding of some glasses was a consequence of inappropriate preparation of material and selection of inappropriate tissue sites, e.g., muscle. When the glass implant is successfully immobilized in appropriate soft tissue during the experimental period and when proper histological specimens are made, soft tissue adhesion to some glasses can be confirmed and evaluated. These particular glass compositions have also been found to advantageously become encapsulated with a thin (i.e., no more than about 1-3 fibers thick) layer of collagen after implantation.